Utilização de adesivos à base de taninos de acácia negra e Eucalyptus pellita para fabricação de painéis OSB

Abstract

The purpose of the present work was to study the viability of the utilization of the tannins of the bark from Acacia mearnsii and of Eucalyptus pellita wood, as adhesive (Tannin- Formaldehyde) for the OSB production. Seven condition of extraction (water at 100ºC, water / 1% urea, water/2% urea, water/5% urea, water/1% sodium sulphite, water/ 2% sodium sulphite and water/5% sodium sulphite) were tested. The chemical properties of the extracts were evaluated and extraction with water/2% urea showed the best quality for adhesive production. Two levels of synthetic resins substitution with the bark extract of Acacia mearnsii were tested (90:10; 80:20). OSB were made with PF-resin, PF resin modified with tannin of acacia and resin of acacia (TF-resin) using two pressing times (6 min and 9 min) and their physical e mechanical properties were measured. OSB were made too with TF resin of acacia modified with tannin of Eucalyptus pellita wood (10% and 20%). The analysis were based on the tests of static bending, tensile strength perpendicular to surface, thickness swelling and water absorption. Modified PF resin made with extracts from acacia bark showed to be suitable for OSB production. Results of the physical and mechanical properties were in according to the European Norm EN 300. OSB made with tannin from acacia bark showed satisfactory results with pressing of 6 min. The substitution of tannin of acacia to tannin of eucalyptus is possible; however the humidity resistance was low.